title: Replication and trafficking of a plant virus are coupled at the entrances of plasmodesmata.
abstract: Plant viruses use movement proteins (MPs) to modify intercellular pores called plasmodesmata (PD) to cross the plant cell wall. Many viruses encode a conserved set of three MPs, known as the triple gene block (TGB), typified by Potato virus X (PVX). In this paper, using live-cell imaging of viral RNA (vRNA) and virus-encoded proteins, we show that the TGB proteins have distinct functions during movement. TGB2 and TGB3 established endoplasmic reticulum-derived membranous caps at PD orifices. These caps harbored the PVX replicase and nonencapsidated vRNA and represented PD-anchored viral replication sites. TGB1 mediated insertion of the viral coat protein into PD, probably by its interaction with the 5' end of nascent virions, and was recruited to PD by the TGB2/3 complex. We propose a new model of plant virus movement, which we term coreplicational insertion, in which MPs function to compartmentalize replication complexes at PD for localized RNA synthesis and directional trafficking of the virus between cells.
authors.affiliation: Biomedical Sciences Research Complex, University of St Andrews, Fife KY16 9ST, Scotland, UK. jt58@st-andrews.ac.uk
authors.forename: Jens
authors.initials: J
authors.lastname: Tilsner
authors.forename: Olga
authors.initials: O
authors.lastname: Linnik
authors.forename: Marion
authors.initials: M
authors.lastname: Louveaux
authors.forename: Ian M
authors.initials: IM
authors.lastname: Roberts
authors.forename: Sean N
authors.initials: SN
authors.lastname: Chapman
authors.forename: Karl J
authors.initials: KJ
authors.lastname: Oparka
mesh_terms: D001692:Biological Transport; D004721:Endoplasmic Reticulum / Q000378:metabolism / Q000648:ultrastructure; D008954:Models, Biological; D009154:Mutation; D053830:Plant Viral Movement Proteins / Q000032:analysis / Q000235:genetics / Q000502:physiology*; D031425:Plasmodesmata / Q000821:virology*; D017863:Potexvirus / Q000502:physiology*; D012367:RNA, Viral / Q000032:analysis / Q000378:metabolism; D012324:RNA-Dependent RNA Polymerase / Q000032:analysis / Q000378:metabolism; D014026:Nicotiana / Q000821:virology; D014779:Virus Replication / Q000502:physiology*
chemical_list: D053830:Plant Viral Movement Proteins; D012367:RNA, Viral; D012324:RNA-Dependent RNA Polymerase